The present invention relates to a decentered optical system having decentered optical surfaces as well as an image projection apparatus and an imaging apparatus, each incorporating a decentered optical system.
So far there has been an image projection apparatus known in the art, which makes use of small-size or compact image display devices to enlarge or scale up original images on these devices through an optical system for projection of the enlarged images (see Patent Publications 1, 2, 3). There is now a mounting demand for this image projection apparatus to be smaller in size and lighter in weight for more enhanced portability. In order to present images, there is also an increasing demand for an optical system capable of enlarging original images on the display devices to a certain degree for projection of them at a wide angle of view and representing them at a high resolution. Some means known to fill such demands include an apparatus in which a projection optical system comprises a decentered mirror that is a concave mirror decentered with respect to the visual axis of a viewer for enlargement and projection of an enlarged virtual image on an image display device.
Patent Publications 1, 2 and 3 each disclose a decentered optical system comprising a first prism having at least one rotationally asymmetric surface and a second prism having an exit surface defined by a convex or concave surface.
Patent Publication 1: JP(A) 9-146037
Patent Publication 2: JP(A) 2002-318366
Patent Publication 3: JP(A) 2013-29704